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Engines Starts then Dies

K

Klink

Regular Contributor
My 1993 Johnson 25hp starts up, runs for a few seconds then turns off, then it's hard to start without using the key switch electrical primer. Before it turns off, if I push the key switch primer in, it keeps running, as long as I keep doing it. After it turns off, I let it sit for 10 minutes, and she starts right up without priming and runs fine till she dies again. Repeat same as above.

It ran fine 10 days ago, but was running hot, so I took the heads off and cleaned the water passages as the passages and thermostat were totally clogged. To get to the bolts I had to completely remove the power pack and ignition coils. I replaced the thermostat with a thermostat that is always open because I cut out the hat. I put in new head gasket, and head cover gasket, and torqued to spec (and now re-torqued to spec after running it). I reconnected all the electrics, finished the job and ran the motor to test it, and I get the result above. I don't see any relation between my work and the engine shutting off do any of you?

It seems like a carb problem but why would it happen now? I'm stumped.
 
You apparently have compression and ignition... that leaves the fuel system.

Yes, what you've had to say indicates that the carburetor requires cleaning. The engine runs as long as fuel is being supplied via the fuel primer solenoid but fuel is not flowing thru the carburetor passageways.

Why is it happening now? A vindictive engine... it never did like you! :cool:
 
I think I got it solved, weird stuff!

Did a spark test, specs call for it to jump a 7/16” gap. I set the spark tester with the caliper gage at 7/16”. TOP CYLINDER barely jumped it. Then did BOTTOM CYLINDER it easily jumped 7/16, so I set it to like 5/8 or maybe 3/4 and it jumped it. Went back and did top cylinder and it would not jump even the 7/16”. I had four of the same coils from the spare 115hp and one passed the Ohmmeter test, so I installed it on the top #1 cylinder. and tested the spark and it jumped past 5/8”.

I also tested the resistance in the spark plug wires and the bottom plug did not even have continuity!

The top cylinder was black again after maybe running it for 3 minutes? The bottom cylinder was the dirty cylinder when I cleaned the heads. Both cylinder tops were cleaned spotless. Now the bottom cylinder was as clean as the day I cleaned it and the top was black.

Tested all the spark plug wires I had from the spare J115 and ALL had no contiunuity! So I used one off the good J115 just to test the J25. I put it on the bottom cylinder.

After all that I tested the engine and it didn’t run much better. I removed the top spark plug wire and the engine ran just the same. Therefore, I changed the spark plug (I had an almost new one on the spare 115hp.

Tested again and it ran better but the carburetor would spit back and want to turn off. I adjust the idle mixture screw out ¼ turn out and it stopped spitting. The did a link & sync on it, except for the high speed timing adjustment (the Joe Reeves Method) since I was rusty on it.

I tested again and it ran fine. I adjusted the idle speed and left the idle mixture screw at about ¼ out from what it was when I bought it, since I could not get it to speed up with the needle and it did spit and turn off anywhere past where it was when I bought it. Let’s see how she runs at high speed.

I’m thinking that the use of a (free) thermostat with the hat cut off is not such a good idea. I ordered a new OEM thermostat. We’ll see how it runs when in high speed, however, I don’t like the fact that it'll never warm up at idle.
 
Klink said:
Let’s see how she runs at high speed. I’m thinking that the use of a (free) thermostat with the hat cut off is not such a good idea. I ordered a new OEM thermostat. We’ll see how it runs when in high speed, however, I don’t like the fact that it'll never warm up at idle.
Click to expand...

I water tested it and it ran great as is. It idles fine once she's warmed up. Runs great at high speed. Will postpone the installation of the thermostat till have to do some other work in the area.
 
(Thermostat Purpose)
(J. Reeves)


Many engines are considered high performance engines and demand a thermostat(s), and many smaller hp engines also require a thermostat for the following reason. The pistons actually distort/twist off round when running. The thermostat is required to keep the outer wall surrounding the steel cylinder, and the cylinder wall itself at a temperature to compensate for the distortion.


With the thermostat removed, the difference in temperature between the inside the cylinder and the water jacket quickly reaches a point whereas (in effect) you have a oblong piston running up and down a round cylinder, or vice versa. Bottom line is without the thermostat, the piston and cylinder wall could be damaged in a short period of time.

The thermostat in your car isn't there simply to have the heater function properly..... think about it.


Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
Its not the stator nor fuel pump. I put it high idle with 3 new plugs she started up. I let her warm up and put her in neautral and just before she was going to conk out i pushed in the key just a little shot and she kept running i kept doing that and i had my neighbor take over and I noticed every time the key would be pushed in, air bubbles would fill about a quarter of the new glass inline filter i put on when i changed out all my fuel lines to and from the choke and to the carbs. Batery voltage was reading 13.8 but i could have kept her going all night this way. Every time me or my buddy gave it that primer just before she wanted to die she wouldn’t but those air bubbles came in from the tank end towards the carbs. Is this now a carb problem with one of the primer solinoid lines?. This whole thing is a trip! Hows that for an update, btw there is good spark i did that test before we started her.
 
Im a little releaved or should i be? This is seeming to be now maybe a simple problem. I had the airbox still on so I couldn’t see the lines. Would a kinked line from That solenoid do that too? Air leak in the solinoid itself where the lines go in maybe?
 
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